1. Field of the Invention
The present invention relates to a combustion-operated setting tool for driving in fastening elements and including a combustion drive for driving a setting piston displaceable in a guide cylinder, a ventilator for the combustion drive, and a control unit for controlling the ventilator.
2. Description of the Prior Art
Setting tools of this kind can be operated, e.g., with gaseous or vaporizable liquid fuels. In combustion-operated setting tools, a setting piston is driven by combustion gases during a setting process. Fastening elements can then be driven into a substrate by the setting piston. In the setting tools of this type, ventilator functions include cooling the setting tool that has been heated by the occurring combustion processes. The cooling is necessary because it is important for the thermal return of the piston, for example, that the combustion chamber wall does not become too hot. Further, excessive heating of the metering valve can lead to faulty metering of the fuel when the setting tool becomes too hot.
US 2005/0173485 A1 discloses a combustion-operated setting tool having a combustion-operated energy source and a ventilator associated with the latter. A control device which is connected to a temperature sensor monitoring the temperature of the energy source is provided for adjusting the operating time. The duration of the operating time of the ventilator can be adjusted by the control device as a function of the temperature of the energy source detected by the temperature sensor.
The disadvantage of providing a temperature sensor consists in a complicated design of the sensor and increased production cost. The temperature sensor must be connected to the control device located in the handle assembly. As the temperature sensor is arranged in the vicinity of the energy source, in particular in the vicinity of the cylinder for the driving piston, long cable paths are required. This makes the combustion-operated setting tool expensive to manufacture.